Explosive rivet detonating tool



Feb. 13, 1968 T. M. JACOBS EXPLOSIVE RIVET DETONATING TOOL 2 SheetsSheei 1 Filed May 13, 1965 1 fry? Feb. 13, 1968 JACOBS 3,369,102

EXPLOSI VE RIVET DETONATING TOOL Filed May 13, 1965 v 2 Sheets-Sheet 2 I2 37 24 as r I II II II II II II I I I United States Patent 3,369,102 EXPLOSIVE RIVET DETONATING TOOL Theodore M. Jacobs, 520 22nd Ave. NW., Calgary, Alberta, Canada Filed May 13, 1965, Ser. No. 455,530 2 Claims. (Cl. 219-234) ABSTRACT OF THE DISCLOSURE A hand-held electrically operated resistance-and-arc heating rivet detonating tool, having a centrally positioned spring-loaded electrode for initially seating the rivet, and a concentrically positioned tubular electrode, also springloaded, for final seating of the rivet, and a pressure-activated contact switch for energizing the tool. The tool makes possible the sequential steps of seating, retaining and detonating of explosive rivets by means of graduated increased pressure of the tool against the rivet, permitting the operation to be aborted at any desired point until the final pressure is applied against the rivet by means of the rivet detonating tool.

The present invention relates to the utilization of explosive rivets, and more particularly to an improved explosive rivet detonating tool.

Explosive rivets are well known in the art, and consist of a head portion and a hollow shank portion filled with a heat-sensitive explosive, adapted to be detonated on the application of an external source of heat. Such rivets are used in locations or applications where, because of the difficulty or impossibility of using a rivet backing tool, a self-expanding rivet is desirable or necessary.

A persistent problem in using explosive rivets is that of seating the rivet and holding it in place prior to its detonation.

Premature detonation results in a poorly seated rivet and creates a risk to the operator of injury.

Heretofore with the conventional type of rivet detonating tool, the rivet is seated, held in place and detonated by means of a heated tool, and once the heated tool is brought into contact with the rivet, the riveting operation must continue, otherwise the operator risks the danger of an unconfined explosion of the rivet.

It is the principal object of my invention to provide a means of seating the rivet and holding it firmly in place prior to the application of the heat required for detonation.

It is a further object of my invention to provide an explosive rivet detonating tool wherein the rivet seat ing means is located forwardly of the rivet detonating assembly, thus adapted to sequentially seat the rivet and hold it in place prior to the detonation of the rivet.

It is a further object of my invention to provide an explosive rivet detonating tool wherein the heat of detonation is generated firstly by the arcing of a relatively high amperage current flow, at the point of contact of the rivet detonating assembly with the rivet, and secondly, by the passage of the current flow through the limited crosssectional area of the rivet head, and thirdly by the heating effect of the current through a rivet contacting tip characterized by its high electrical resistivity.

It is a further object of my invention to provide an explosive rivet detonating tool wherein the rivet seating means and the rivet detonating assembly are each independently spring biased forwardly for limited axial movement and incorporate an electrical contact completing 3,369,102 Patented Feb. 13,, 1968 the heating circuit and thereby providing the heat of detonation.

It is a further object of my invention to provide an explosive rivet detonating tool wherein the rivet head engaging portions are constructed of metal characterized by high impact and wear resistance and low heat con-' ductivity.

A still further object of my invention is to provide an explosive rivet detonating tool which is light and convenient and durable in use, and inexpensive in manufacture.

My invention consists of an explosive rivet detonating tool adapted to detonate an explosive rivet through heat applied in and through the head of said rivet by means of a relatively high amperage electrical current, by the sequential steps of bringing a spring-biased rivet seating pin having high electrical resistance at its tip into initial contact with said rivet head and applying rivet seating pressure through said pin, then through application of further pressure bringing a spring-biased rivet contacting sleeve, circumferentially located around and electrically insulated from said pin, into contact with said rivet head, and then through still further pressure, completing the electrical circuit and thereby permitting an electrical current of relatively high amperage to flow through said circuit, creating rivet detonating heat by combination of resistance and arcing, said tool being adapted to rapid successive reuse without danger of premature detonation inherent in high residual heat stored in the rivet seating and detonating assembly.

The manner in which my invention attains the objects first set out above and overcomes the disadvantages of the former practice, will become apparent as the description proceeds, the invention residing in the construction, combination and arrangement of parts hereinafter more fully described and claimed, and illustrated in the accompanying drawings, in which like characters of reference indicate like parts through the several figures, and in which:

FIGURE 1 represents a perspective view of the eX- plosive rivet detonating tool.

FIGURE 2 represents a cross-sectional view of the tool, showing the arrangement of the respective components, and the rivet seating means in engagement with a rivet head.

FIGURE 3 represents a partially cross-sectional view of the tool, showing the arrangement of the respective components, and the rivet seating means in engagement with a rivet head.

FIGURE 4 represents the rivet seating means and rivet detonating assembly, in enlarged cross-sectional detail.

Referring more particularly to the drawings, in FIG- URE 1 the device is comprised of a handle portion 10 of convenient size and configuration adapted to be held in one hand of the operator, and constructed of material having heat and electrical insulating qualities, such as high temperature plastic. The handle portion may be conveniently made in two symmetrical halves for ease of construction, assembly and repair, the two halves being generally designated 14.

The rivet seating pin 13 consists of a metal shank portion 15, desirably of metal construction having good electrical conductivity, such as copper; a pin portion 16, screw mounted at the forward end of the cylindrical portion 15, and desirably constructed of stainless steel, adapted to receive the insertion tip portion 17, constructed of metal having high electrical resistance, such as nickelchromium alloy, which will heat with the passage of electrical current therethrough to a temperature of the order of 8001000 F.

Positioned at the rearward extremity of the rivet seating pin is a spring 18, in compression contact between the rear face of the pin and an electrical contact disc 19, attached to the rivet seating pin by means of a flexibly extensible conductor 20, of braided copper wire or the like. Mating with the electrical contact 19 is a corresponding contact 21 connected by means of the conductor 22 to one of the connectors 11.

Circumferentially located around and co-axial with the rivet seating pin 13 is the rivet contacting sleeve assembly, generally designated 14, which consists firstly of the inner barrel 23 of electrically insulating material adapted to enclose pin 13 as a journal bearing and thereby support it for limited longitudinal movement, and also to insulate it from the rest of the rivet contacting sleeve assembly 14; and further consists of the outer barrel 24, desirably of metal having good electrical conductivity such as copper; and the tip assembly generally designated 25, screw threaded into the outer barrel 24 and itself consisting of the contactor portion 26, and the insulating sleeve 27 as illustrated in FIGURE 4. Desirably the contactor portion 26 is constructed of hard metal, such as stainless steel, having better heat resistance qualities than the outer barrel portion 24, and being wear resistant; the insulator 'sleeve 27 is constructed of high temperature resistance electrically non-conductive plastic material.

Integral with and forming part of the outer barrel 24 is the lug element 28, with electrical contact 29 thereon, adapted to mate with corresponding contact 30, connected to conductor 31, which is in turn connected to the second of the pair of electrical connectors 11.

Positioned rearward of the rivet contacting sleeve assembly 14 is a spring 32, incompression contact with the shoulder 33 of the handle housing and adapted to urge the rivet contacting sleeve assembly forward. Forward movement of the rivet contacting sleeve assembly is arrested by contact of the lug element 28 with the stop face 34 integral'with the handle housing, while forward movement of the rivet seating pin 13 is arrested by contact of the shoulder 35 with the stop face 36 formed on the insulator sleeve 27, as illustrated in FIGURE 4.

The diameter of the forward opening of the rivet contacting sleeve assembly is slightly smaller than the diameter of the head of the rivet 37, so as to peripherally engage the rivet head when in pressure contact with it as illustrated in FIGURE 3.

The inner dimension of the handle and housing portion is such as to provide a sliding fit around the outer barrel 24 and the rearward extension of the inner barrel 23 of the rivet contacting sleeve assembly, and the exposed portion of the rivet seating pin 13, as illustrated in FIG- URE 3.

The tip portion 16 of the rivet seating pin 12 being screw threaded and removable, may be replaced when excessive wear occurs, The contact portion 26 of the rivet contacting sleeve assembly 14, being screw threaded, is removable and thereby provides for a plurality of tip sizes necessary in the working of different sized rivets.

The operation of my device in conjunction with an explosive rivet and associated plates is illustrated in FIG- URE 3, which shows the co-operative relationship of the assembly relative to the rivet.

The tip 17 is centred on the rivet head to be riveted and one electrical contact is thereby established between the rivet seating pin and the rivet head. Forward pressure on the tool exerted by the operator results in the rivet thus engaged being seated in the rivet hole. Further pressure on the tool results in compression of the spring 18 and rearward movement of the pin 13 against the spring bias, thereby exerting further seating pressure on the rivet, and bringing the rivet head into engagement with the contact portion 26 of the rivet contacting sleeve assembly. Further forward pressure exerted by the operator results in an additional seating load on the rivet, and compresses the sleeve assembly spring 32 in response to the rearward movement of the sleeve assembly relative to and around the rivet seating pin, until electrical contact is made between the two contact elements 29 and 30, thereby completing the circuit, whereupon current is enabled to flow through the heating tip of the rivet seating pin and the rivet head, making arcing contact with the contact portion 26 of the sleeve assembly. The combined momentary heating effect produced thereby results in a virtually instantaneous increase in temperature of the rivet head, and the consequent detonation of the explosive charge in the rivet. In this position of the tool, the rivet head is fully surrounded by the rivet sleeve assembly and the rivet detonation is accurately controlled as there can be no accidental heating of the rivet.

I have found that a current of the order of 60 to amperes is sufficient for most conventional uses, in conjunction with an applied voltage of 20 volts.

Because of the relatively low heat conductivity of the component parts in actual engaging contact with the heated rivet head, the heated masses are isolated and therefore rapidly cool between successive applications of the tool.

It is to be observed that the riveting sequence can be safely aborted at any time, up until the last moment when the final application of pressure completes the electrical circuit and initiates the arcing and heating.

What I claim as my invention is:

1. An explosive rivet detonating tool adapted for use with explosive metal rivets comprising in combination an electrical and heat insulating handle portion, a rivet seating and detonating assembly mounted for limited longitudinal movement adjacent to the forward end of said handle portion, a first and second of electrical conductor each connected to an external source of electrical energy, said electrical conductors extending into said handle portion, said rivet seating and detonating assembly comprising a rivet seating pin having a heating tip located on its forward end, said heating tip adapted to heat in response to the flow of electrical current therethrough, and said rivet seating pin being spring biased forward for longitudinal limited axial movement, and a flexibly extensible electrical conductor connected to said rivet seating pin adapted for electrical connection with the first of said electrical conductors, said rivet seating and detonating assembly further comprising a rivet contacting sleeve circumferentially located around and co-axial with said rivet seating pin and mounted for limited longitudinal axial movement within said handle portion, said rivet contacting sleeve comprising an electrically insulating inner barrel adapted to slidingly engage said rivet seating pin, an electrically conductive outer barrel circumferentially engaging said inner barrel, a tip assembly adapted to operatively connect with said inner and outer barrels consisting of an inner electrically insulating sleeve slidingly engaging said rivet seating pin and an outer electrically conductive contactor portion, said rivet contacting sleeve assembly being spring biased forwardly relative to said handle portion, a first electrical contact mounted on said rivet contacting sleeve assembly and longitudinally moveable therewith, a second electrical contact mounted on said insulating handle portion and electrically connected to said second electrical conductor, said first and second electrical contacts being normally spaced apart and adapted to make mutual contact when said rivet contacting sleeve assembly moves rearwardly relative to said handle 5 portion upon application of pressure to the forward end of said rivet contacting sleeve assembly when operatively engaging the head of one of said rivets, to complete the electrical circuit through the rivet detonating tool.

2. The device as defined in claim 1 wherein said rivet seating pin comprises a metal tip portion, a metal shank portion connected to said tip portion, and an electrical conductor portion connected to said shank portion, said tip portion being of nickel-chromium alloy, said shank portion being of steel, and said conductor portion bein of copper.

References Cited UNITED STATES PATENTS Fassler 219-86 Dyer 219-86 Hu rlebaus 219-86 Navlty et a1 219-234 X Obolensky 219-234 X Handley 219-234 10 ANTHONY BARTIS, Primary Examiner. 

